Structural basis of carbohydrate transfer activity by human UDP-GalNAc: polypeptide alpha-N-acetylgalactosaminyltransferase (pp-GalNAc-T10)

J Mol Biol. 2006 Jun 9;359(3):708-27. doi: 10.1016/j.jmb.2006.03.061. Epub 2006 Apr 19.

Abstract

Mucin-type O-glycans are important carbohydrate chains involved in differentiation and malignant transformation. Biosynthesis of the O-glycan is initiated by the transfer of N-acetylgalactosamine (GalNAc) which is catalyzed by UDP-GalNAc:polypeptide alpha-N-acetylgalactosaminyltransferases (pp-GalNAc-Ts). Here we present crystal structures of the pp-GalNAc-T10 isozyme, which has specificity for glycosylated peptides, in complex with the hydrolyzed donor substrate UDP-GalNAc and in complex with GalNAc-serine. A structural comparison with uncomplexed pp-GalNAc-T1 suggests that substantial conformational changes occur in two loops near the catalytic center upon donor substrate binding, and that a distinct interdomain arrangement between the catalytic and lectin domains forms a narrow cleft for acceptor substrates. The distance between the catalytic center and the carbohydrate-binding site on the lectin beta sub-domain influences the position of GalNAc glycosylation on GalNAc-glycosylated peptide substrates. A chimeric enzyme in which the two domains of pp-GalNAc-T10 are connected by a linker from pp-GalNAc-T1 acquires activity toward non-glycosylated acceptors, identifying a potential mechanism for generating the various acceptor specificities in different isozymes to produce a wide range of O-glycans.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Carbohydrates / chemistry*
  • Catalytic Domain
  • Crystallography, X-Ray
  • Glycosylation
  • Humans
  • Isoenzymes / chemistry
  • Isoenzymes / genetics
  • Manganese / chemistry
  • Models, Molecular*
  • Molecular Sequence Data
  • Mucins / chemistry
  • Mutation
  • N-Acetylgalactosaminyltransferases / chemistry*
  • N-Acetylgalactosaminyltransferases / genetics
  • Protein Binding
  • Protein Structure, Tertiary
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / genetics
  • Substrate Specificity
  • Uridine Diphosphate / chemistry

Substances

  • Carbohydrates
  • Isoenzymes
  • Mucins
  • Recombinant Proteins
  • Manganese
  • Uridine Diphosphate
  • N-Acetylgalactosaminyltransferases
  • polypeptide N-acetylgalactosaminyltransferase

Associated data

  • PDB/2D7I
  • PDB/2D7R